Looters stormed the weapons site at Al Qaqaa in the days after American troops swept through the area in early April 2003 on their way to Baghdad, gutting office buildings, carrying off munitions and even dismantling heavy machinery, three Iraqi witnesses and a regional security chief said Wednesday.

The Iraqis described an orgy of theft so extensive that enterprising residents rented their trucks to looters. But some looting was clearly indiscriminate, with people grabbing anything they could find and later heaving unwanted items off the trucks.

Two witnesses were employees of Al Qaqaa - one a chemical engineer and the other a mechanic - and the third was a former employee, a chemist, who had come back to retrieve his records, determined to keep them out of American hands. The mechanic, Ahmed Saleh Mezher, said employees asked the Americans to protect the site but were told this was not the soldiers' responsibility.

The accounts do not directly address the question of when 380 tons of powerful conventional explosives vanished from the site sometime after early March, the last time international inspectors checked the seals on the bunkers where the material was stored. It is possible that Iraqi forces removed some explosives before the invasion.

But the accounts make clear that what set off much if not all of the looting was the arrival and swift departure of American troops, who did not secure the site after inducing the Iraqi forces to abandon it.

"The looting started after the collapse of the regime," said Wathiq al-Dulaimi, a regional security chief, who was based nearby in Latifiya. But once it had begun, he said, the booty streamed toward Baghdad.

Earlier this month, on Oct. 10, the directorate of national monitoring at the Ministry of Science and Technology notified the International Atomic Energy Agency that the explosives, which are used in demolition and missiles and are the raw material for plastic explosives, were missing. The agency has monitored the explosives because they can also be used as the initiator of an atomic bomb.

Agency officials examined the explosives in January 2003 and noted in early March that their seals were still in place. On April 3, the Third Infantry Division arrived with the first American troops.